Plan Your Route: avoid migrating mailboxes to O365 the hard way

February 2, 2018


Consider this scenario: you are a small-to-medium sized company and have decided to migrate your users and associated data to Microsoft’s Office 365 (O365) service, from an exchange platform with associated AD infrastructure.

Many are making this move and considering a cutover migration. But there’s a trap! One that if you fall into could cost time and money by making your full migration hard and very manual.

If you look online you’ll see there are synchronisation tools to save having to rebuild all your users. Azure Active Directory Connect (AADC) from Microsoft, seems ideal. Your users will be setup in O365 without having to manually create them, and will be able to start using some of the O365 services and features, such as Skype for Business and SharePoint Online, before you have to worry about migrating data.

But wait. If you continue down this path, you could end up having to jump through a whole range of hurdles.

“…avoid travelling the hard path to O365.”

Whilst setting up AADC is very beneficial, doing so before you migrate your email data can cause significant issues as you will be unable to use the migration tools available in Exchange Online, or indeed from a third party, to migrate your email data.

If you go down the AADC route before migrating your email data, your only options are as follows:

Disable AADC synchronisation and remove all user accounts from O365
This could cause significant disruption to your users, especially if they have been using the O365 services for some time.

A manual export/import of email data
This involves exporting all data from your current mailboxes to pst files, uploading these to a Microsoft Azure storage account (which may incur a subscription charge) and then importing the data from there into the corresponding O365 mailbox. This process can take a very long time to complete, may have to be run more than once, and requires manual creation in O365 of other Exchange objects, such as distribution lists and global contacts.

An IMAP migration
This method does automate some of the migration, but will only target email folders in your user mailboxes. Other non-email content, such as calendar items and tasks, must be migrated using the manual export/import method described above. You will also have to manually create other Exchange objects, such as distribution lists and global contacts.

The better option is to migrate your data first, before enabling AD synchronisation. There are tools that can be used to make the move to Office 365 much easier and there is a strong business case for exploring what is available or speaking to a partner who can help you navigate your migration most effectively.

In short, time and effort spent in the planning stage will help you make the right decisions for your requirements and environment. Migrating your data first, before enabling AD synchronisation, will put you in the best possible position to avoid travelling the hard path to O365.


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